Conference puts health in the spotlight

September 27 2017

This year's Arboricultural Association conference teamed up with The Chartered Institute of Ecology and Environmental Management (CIEEM) to take a global look at tree biosecurity.

It is a measure of the importance attached to the future health of the UK's trees that HRH The Prince of Wales readily agreed to prepare a message of support to open the 2017 Arboricultural Association (AA) national conference.

The 51st annual three-day event, for the first time run in collaboration with CIEEM, returned to Exeter University this year to turn the spotlight on tree health and sustainability. AA chairman Keith Sacre talked of the collaborative approach required to succeed in the fight against pests and diseases and the importance of a global approach, highlighting the international line-up of speakers for the conference.

A world view

JPA's Jeremy Peirce was there for two days to hear the latest thinking. The Tuesday sessions covered diversity, ecology and tree selection and environmental management in practice. The speakers were drawn from many sectors both in the UK and overseas and covered a wide variety of topics including balancing veteran tree management, habitat-recreation and public access in the face of biosecurity threats; examining what kind of treescape we want and can expect; and managing the urban forest.

It was good to be able to view our day-to-day work in a slightly different context: trees are complex organisms and it is important to remember that the issues we cover have implications outside of pure arboriculture. The morning session ended with a talk from Ted Green, one of the world's leading authorities on ancient trees and a man never afraid to speak his mind. His presentation touched on the potential effects of Brexit and the challenging issues we will face trying to manage tree diseases in isolation. His view was that we are part of Europe whether we like it or not and if we are to make any realistic progress we will need to work with our European colleagues.

Worrying outlook for ash

The Wednesday sessions covered pests and diseases as well as biomechanics and morphology. Keeping abreast of P&D developments and current understanding is vital and to hear that from some of the world's leading scientists means that we can pass on the most up to date information to our clients.

Jon Stokes, programme director at The Tree Council, gave an excellent overview of the latest details and research on Chalara dieback of ash (Hymenoscyphus fraxineus). Of all the current tree diseases (and there are many) dieback and the impact it will potentially have on our ash trees is particularly worrying.

The Devon Ash Dieback Action Plan (which has been widely acknowledged as being one of the best management documents) states: 'Ash is one of the most abundant trees in Devon. Best available figures suggest there are at least 1.9 million full grown or nearly mature ash trees outside woodlands in the county: ash is our second most numerous hedgerow tree. Ash-dominated woodland covers about 11,000 ha, 22% of all broadleaved woodland.

'The current consensus is that levels of mortality or severe dieback symptoms will be high within woodlands. However, the impact of the disease in non-woodland situations is far less certain and may be less severe. Many factors including the density of trees, their age, genetic variability and climatic conditions are likely to influence the impact. In a worse case situation, 90% of non-woodland trees may be affected over the next 10 to 20 years to the extent that they will at least shed large limbs. The current consensus is that it is more likely that 30-50% of trees will be damaged to this extent over the same time period.'

Over the next decade or so it is likely that our work as arb professionals will be heavily influenced by the management of ash dieback, which is already making an appearance in Devon's landscape. I took the photo above just outside Tiverton a few weeks ago - it shows a typical 'diamond' shaped lesion that is easy to see on small regrowth but is not so easy to spot on mature trees. Jon Stokes' talk and our own observations suggest that while ash dieback will kill young trees reasonably quickly, mature trees will take longer to die and that we are likely to see a protracted decline in the health of mature ash trees over a number of years.